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A240034
Number of n X 3 0..2 arrays with no element equal to zero plus the sum of elements to its left or zero plus the sum of elements above it or zero plus the sum of the elements diagonally to its northwest, modulo 3.
1
4, 6, 16, 16, 42, 44, 114, 122, 314, 340, 872, 950, 2432, 2658, 6798, 7442, 19024, 20844, 53270, 58392, 149210, 163594, 418006, 458356, 1171124, 1284250, 3281268, 3598338, 9193694, 10082246, 25759848, 28249720, 72177042, 79153804, 202234930
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 4*a(n-2) - 3*a(n-4) -a(n-6) for n>7.
Empirical g.f.: 2*x*(2 + 3*x - 4*x^3 - 5*x^4 - x^5 - x^6) / (1 - 4*x^2 + 3*x^4 + x^6). - Colin Barker, Oct 27 2018
EXAMPLE
Some solutions for n=3:
..1..2..1....1..2..1....2..1..1....2..1..2....1..2..2....2..1..2....2..1..1
..2..0..0....2..0..0....1..0..0....1..0..0....2..0..0....1..0..0....1..0..0
..2..1..2....1..0..0....1..0..0....2..0..0....2..0..0....1..0..0....2..0..0
CROSSREFS
Column 3 of A240039.
Sequence in context: A278239 A328965 A133092 * A302122 A056222 A186201
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 31 2014
STATUS
approved